Array also implements IReadOnlyList if I'm not mistaken.
I think C# doesn't really have immutable collections, they just can be typecasted to IReadonly* to hide the mutable operations. But they can always be typecasted back to their mutable base implementation.
The only real immutable collections I know of, are F#s linked lists.
Immutable collections exit, they were just added later. See System.Collections.Immutable:
https://learn.microsoft.com/en-us/dotnet/api/system.collecti...
Those collections are more like copy-on-write than actual immutable. System.Collections.Frozen is the real thing.
Isn't Frozen something you do to a set or dictionary to say, I'm not going to add any more values, please give me a version of this which is optimized for lookup only?
I do a lot of .NET programming, and I've never seen them getting used. :O
Roslyn, the C#/VB compiler, uses them extensively, but in other code they're indeed quite rare.
Adding to the sibling comment, there are also Frozen{Dictionary,Set}: https://learn.microsoft.com/en-us/dotnet/api/system.collecti...
One man's constant is another man's variable.
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